Distributed operating system: Difference between revisions

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|style="background:#DFFFFF;width:400px;"|'''Added rough draft of "Overview" section...'''<br />&nbsp;&nbsp;&nbsp;[[User:JLSjr|JLSjr]] ([[User talk:JLSjr|talk]]) 06:45, 17 March 2010 (UTC)

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== Overview ==

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An approach to describing the unique nature of DOS

<br />{{pad|2em}} A Distributed OS is decentralized, but has additional specific attributes; it is distributed

<br />{{pad|4em}} compared to a standard OS which is centralized and local

<br />{{pad|4em}} or a Network OS which is decentralized, and while possibly spatially scattered, is not distributed

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The unique nature of the Distributed operating system is both subtle and complex. A distributed operating system’s hardware infrastructure elements are not centralized, that is the elements do not have a tight proximity to one another at a single ___location. A given distributed operating system’s structure elements could reside in various rooms within a building, or in various buildings around the world. This geographically spatial dissemination defines its decentralization; however, the distributed operating system is a distributed system, not simply decentralized.

<br />{{pad|2em}} to demonstrate, consider an OSs constituent element organization: decentralized vs. distributed

<br />{{pad|4em}} three tightly interrelated aspects to this organization:

This distinction is the source of the subtlety and complexity. While decentralized systems and distributed systems are both spatially diverse, it is the specific manner of and relative degree in linkage between the elements, or nodes in the systems that differentiate the two. In the case of these two types of operating system, these linkages are the lines of [[Inter-process communication|communication]] between the nodes of the system.

<br />{{pad|6em}} organizational hierarchy, degree of interconnection, sphere of control

<br />{{pad|4em}} organizational hierarchy:

To better illustrate this point, let us more closely reflect upon these three system [[Software architecture|architectures]]; centralized, decentralized, and distributed. In this examination, we will consider three tightly-related aspects of their structure: organization, connection, and control. Organization will describe physical arrangement characteristics, connection will involve associations among constituent structural entities, and control will correlate the manner, necessity, and rationale of the earlier considerations.

<br />{{pad|6em}} centralized:

<br />{{pad|8em}} dictatorship - one level

<br />{{pad|8em}} all entities report directly to one higher-level entity

<br />{{pad|6em}} decentralized:

<br />{{pad|8em}} federated - one or more levels

<br />{{pad|8em}} any given sub-level's entities reporting directly to next higher-level entity

<br />{{pad|6em}} distributed:

<br />{{pad|8em}} autonomous - no levels required

<br />{{pad|8em}} all entities reporting directly/indirectly to an appointed coordinator

<br />{{pad|4em}} degree of interconnection:

<br />{{pad|6em}} centralized:

<br />{{pad|8em}} single direct connection

<br />{{pad|10em}} balloons on a string

<br />{{pad|6em}} decentralized:

<br />{{pad|8em}} single direct/indirect connection

<br />{{pad|10em}} corporate org-chart (no dotted lines)

<br />{{pad|10em}} twigs, limbs, branches of a tree

<br />{{pad|6em}} distributed:

<br />{{pad|8em}} multiple direct/indirect connections possible

<br />{{pad|10em}} string art, spiro-graph (completely connected)

<br />{{pad|10em}} spider web (closest neighbors)

<br />{{pad|10em}} interstate system (suited to purpose)

<br />{{pad|4em}} sphere of control:

<br />{{pad|6em}} centralized:

<br />{{pad|8em}} direct and absolute

<br />{{pad|6em}} decentralized:

<br />{{pad|8em}} shared by level, through delegation and follow-up

<br />{{pad|6em}} distributed:

<br />{{pad|8em}} collective, usually through mutual agreement

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{{Userbox

<br />{{pad|2em}} DOS is an OS with a unique set of constitutional characteristics

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<br />{{pad|4em}} providing opportunity for an exceptional array of additional and extended services

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<br />{{pad|4em}} while overcoming extreme quantities and degrees of complexity in the process

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|info=Multiple Diagrams<br /><br />will be furnished to assist<br /><br />in illustration of these ideas.

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Firstly, we consider the subject of organization. A centralized system is organized most simply, basically one real level of structure and all constituent element’s highly influenced by and ultimately dependent upon this organization. The Decentralized system is a more [[Federation|federated structure]], multiple levels where subsets of a system’s entities unite, these entity collections in turn uniting at higher levels, in the direction of and culminating at the central element. The distributed system has no discernable or necessary levels; it is purely an autonomous collection of discrete elements.

Association linkages between elements will be the second consideration. In each case, physical association is inextricably linked (or not), to conceptual organization. The centralized system has its constituent members directly united to a central entity. One could conceptualize holding a bunch of [[balloon|balloons]] -- each on a string, -- with the hand being the central figure. A decentralized system incorporates a single-step direct, or multi-step indirect path between any given constituent element and the central entity. This can be understood by thinking of a [[Org_chart#Example_of_an_organizational_chart|corporate organizational chart]], the first level connecting directly, and lower levels connecting indirectly through successively higher levels (no lateral “dotted” lines). Finally, the distributed system has no inherent pattern; direct and indirect connections are possible between any two given elements of the system. Think of the 1970’s phenomena of “[[string art]],” a [[spirograph]] drawing, a [[spider web|spider’s web]], or the [[Interstate Highway System]] between U.S. cities.

Notice, that the centralized and decentralized systems have distinctly directed flows of connection towards the central entity, while the distributed system is in no way influenced specifically by virtue of its organization. This is the pivotal notion of the third consideration. What correlations exist between a system’s organization, and its associations? In all three cases, it is an extremely delicate balance between the administration of processes, and the scope and extensibility of those processes; in essence is about the sphere of control. Simply put, in the directed systems there is more control, easing administration of processes, but constraining their possible scope. On the other hand, the distributed system is much more difficult to control, but is effectively limited in extensible scope only by the capabilities of that control. The associations of the distributed system conform to the needs of its processes, and not inherently in any way to its organizational configuration. There are key collections of extended distributed operating system processes discussed later in this article.

Lastly, as to the nature of the distributed system, some experts state that the distributed operating system is not an operating system at all; but just a distributed system, because of the attention required in maintenance of the system. This author, and by extension this article, will maintain the operating system status of the distributed operating system, by both observation and vacuous proof. As mentioned earlier, a [[Square_(geometry)#Other_facts|square]] is a [[rectangle]]; and no level of effort on its behalf required to maintain four equivalent dimensions affects that fact.

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== Architectural features ==